There have been various theoretical studies done on anisotropic neo-Hookean models; however, there have been limited experimental validations of these theories. In this study, a silicone/silicone laminate with a fiber volume fraction of 18% has been parameterized. Conventional neo-Hookean models have been modified for compressible in-plane deformations. Two-dimensional deformation limitations and a compressible constraint have been discussed. Material parameters have been calculated for three different anisotropic, neo-Hookean models from the literature.

This research details a novel method of increasing the shear yield stress of magnetorheological (MR) fluids by combining shear and squeeze modes of operation to manipulate particle chain structures, to achieve so-called compression-assisted aggregation. The contribution of both active gap separation and particle concentration are experimentally measured using a custom-built Searle cell magnetorheometer, which is a model device emulating a rotary Magnetorheological Energy Absorber (MREA). Characterization data from large (1 mm) and small (250 μm) gap geometries are compared to investigate the effect of the gap on yield stress by compression enhancement. Two MR fluids having different particle concentrations (32 vol% and 40 vol%) are also characterized to demonstrate the effect of solids loading on compression-assisted chain aggregation. Details of the experimental setup and method are presented, and a chain microstructure model is used to explain experimental trends. The torque resisted by practical rotary MREAs is directly related to the strength of the MR fluid used, as measured by the shear yield stress. This study demonstrates that it is feasible, utilizing the compression-enhanced shear yield stress, to either (1) design a rotary MREA of a given volume to achieve higher energy absorption density (energy absorbed normalize by device volume), or (2) reduce the volume of a given rotary MREA to achieve the same energy absorption density.

Dielectric Elastomers (DEs) are incompressible rubber-like solids whose electrical and structural responses are highly nonlinear and strongly coupled. Thanks to their coupled electro-mechanical response, intrinsic lightness, easy-manufacturability and low-cost, DEs are perfectly suited for the development of novel solid-state polymeric energy conversion units with capacitive nature and high-voltage operation, which are more resilient, lightweight, integrated, economic and disposable than traditional generators based on conventional electromagnetic technology. Inflated Circular Diaphragm DE Generators (ICD-DEGs) are a special embodiment of polymeric transducer which can be used to convert pneumatic energy into usable electricity. Potential application of ICD-DEGs is as Power Take-Off (PTO) system for wave energy converters based on the Oscillating Water Column (OWC) principle. This paper presents a reduced, yet accurate, dynamic model for ICD-DEGs which features one degree of freedom and which accounts for DE visco-elasticity. The model is computationally simple and can be easily integrated into existing wave-to-wire models of OWCs to be used for fast analysis and real-time applications. For demonstration purposes, integration of the considered ICD-DEG model with a lumped-parameter hydrodynamic model of a realistic OWC is also presented along with a simulation case study.

Piezoelectric film sensors such as polyvinylidene flouride (PVDF) generate an electrical voltage in response to an applied mechanical stress with a remarkably high sensitivity. They provide very fast response times and do not require extensive signal conditioning. This paper presents a straightforward method of measuring the speed of sound in solid materials and structures using commercial PVDF sensors. PVDF sensors are most commonly used to measure stresses applied in the sensors’ thickness direction. However, this requires that the sensors be located in the load path, which may result in damage to the sensor or affect the response of the system. In this paper, two PVDF sensors are bonded to the side of a structure and a small impact is applied to one end. The sensors are used to measure the time for the impact-induced plane stress wave to travel between the sensors. The observed speed of the propagating stress wave is shown to be in good agreement with the theoretical speed of sound for the material and finite element calculations. In addition, the finite element simulations confirm the validity of the plane wave assumption for non-ideal and non-uniform impact inputs.

In this work, we present results on mathematical modelling of polymeric yield stress fluids which have the properties of both elastic solids and fluids. Our research is based on the approach of multiphase continuum mechanics. A two-phase solid-fluid model is developed. This model is thermodynamically compatible and its governing differential equations can be written in a conservative form. Such a model is convenient for application of advanced high-accuracy numerical methods and modelling of discontinuous solutions such as shock waves and contacts.

Magnetorheological fluids consist of micron sized iron particles mixed in a carrier fluid, and are commonly used in adaptive dampers. Current simulations of MR fluids have been limited to thousands of particle and have been unable to simulate a a practical fluid volume (∼ mm 3 ) with a high solids loading (∼ 25 vol %). In this paper, we use NVIDIA’s CUDA programming environment to simulate over one million particles. Using these simulations, we can dynamically simulate chain formation and restructuring in a practical millimeter scale fluid volume with realistic solids loading. The chain structures can be characterized in terms of extent and number, as well as obtaining physical metrics such as yield stress.

This paper introduces the concept of hydrogel encapsulated interface bilayers as a novel approach for creating durable encapsulated biomolecular materials. The regulated attachment method (RAM) is used to form encapsulated interface bilayers from lipid-encased aqueous volumes contained in a deformable supporting substrate. Physically-encapsulated interface bilayers exhibit increased durability and portability over droplet interface bilayedrs and RAM enables the in situ bilayer formation without the need to dispense and arrange individual droplets. The results presented in this paper demonstrate that poly(ethylene glycol) dimethacrylate monomers (PEG-DMA, M w = 1000), a photopolymerizable hydrogel monomer, and Irgacure 2959 photoinitiator can be incorporated into the aqueous phase in order to form hydrogel encapsulated interface bilayers. Following bilayer formation, exposure to an ultraviolet (UV) light initiates photopolymerization of the polymer on both sides of the bilayer, creating interface bilayers between solid aqueous phases. Electrical recordings of bilayer formation in the liquid state confirm that interface bilayers formed from photopolymerizable aqueous solutions have both high electrical resistances > 1GΩ necessary for observing transmembrane protein gating and survive the UV curing procedure required to polymerize the hydrogel. Photopolymerization for 60 seconds using a 1W hand held UV spot cure light produced water-swollen solids on both sides of the membrane. Hydrogel encapsulated interface bilayers last for hours to days and retain the fluidity necessary for delivering alamethicin proteins to the interface.